The present invention relates to a method of controlling the endfill of tobacco articles.
More specifically, the present invention relates to a method of controlling the endfill of cigarettes, to which the following description refers purely by way of example.
The endfill of cigarettes is normally controlled, as the cigarettes are conveyed side by side, by sensors for determining the presence of tobacco in a given end portion of each cigarette. The sensors may be capacitive, optical, inductive, etc., and are located along a path of the cigarettes, close to one end of the cigarettes. As the ends of the cigarettes are not normally aligned perfectly and are therefore variously positioned with respect to the sensors, the sensor readings are affected by the distance between the sensors and the ends being controlled.
One known solution to the problem is to correct the axial position of the cigarettes via mechanical means, such as inclined surfaces, for pushing the cigarettes into line as they are fed forward. The impact or sliding movement imposed on the cigarettes by such mechanical means, however, may result in damage to the cigarettes.
Another known solution is to determine the position of the ends of the cigarettes by means of a first optical sensor, as a succession of side by side cigarettes is fed along a given path; subject one end of each cigarette frontally to a beam of electromagnetic radiation parallel to the axis of the cigarette; and, finally, determine, by means of a second sensor, the radiation reflected by the surface of said end to generate a corresponding signal characteristic of the endfill of each cigarette.
The reading of the second sensor is corrected, taking into account the distance between the end of each cigarette and the second sensor, by means of a mathematical algorithm based on a physical model or test data; and a reject signal is generated in the event the characteristic signal is below a given threshold value.
The above front control method, however, fails to determine any cavities beneath an apparently satisfactory end surface, and involves mathematically correlating heterogeneous quantities such as the distance between the sensor and the ends of the cigarettes, and the quantity of light reflected.